1 Samuel 17:51

Therefore David ran and stood upon the Philistine Upon his carcass, as it lay prostrate on the ground, and trampled on him, in just contempt of him who had defied, reproached, and despised the armies of Israel:

and took his sword, and drew it out of the sheath thereof; which no doubt was a very large one, and required a good deal of strength to unsheathe it, and use it; and therefore either David, though so very young, was naturally very strong, or he had at this time a more than ordinary measure of strength given him:

and slew him; for it seems that by the blow of the stone he was only stunned, and fell to the ground, but still had life in him, which David soon put an end to by his own sword:

and cut off his head therewith; by which it would appear to both armies looking on that his business was done, and he was thoroughly dispatched:

and when the Philistines saw their champion was dead; of which the cutting off his head was a demonstrative proof, and which they could discern at a distance:

they fled; being struck with a panic at this unexpected event, and no doubt by the Lord; for otherwise, had they given themselves the least time to reflect on their own numbers and strength, they had no just occasion to flee; their safety not depending on a single man, though ever so strong: upon this occasion David penned the ninth psalm; see ( Psalms 9:1-20 ) .